1. Technical Field
The present invention relates to a multi-part sprocket assembly.
2. Description of the Related Art
Agricultural combines typically have removable heads wherein each of the heads is designed for use with a particular crop. A conventional combine head includes a reel and a reciprocating knife cutter bar to cut the crop. An auger then moves the cut crop toward the center of the header. A feederhouse supports the header and receives the cut crop in a conventional combine. The feederhouse then lifts the cut crop and moves it rearward into a threshing mechanism in the body of the combine. A conventional feederhouse includes a chain and lift elevator that carries the crop to the threshing mechanism. The threshing mechanism separates the grain from the chaff and typically utilizes a rotating drum in the threshing process.
Feederhouses conventionally include a shaft having multiple sprockets wherein the sprockets are engaged with the chains of the feederhouse to drive the lift elevator and chains of the feederhouse. The sprockets are subject to wear and periodically fail. Failure of one of the sprockets will generally prevent the combine from operating properly and appropriate repairs must be made before the combine can be returned to service. Repair of a conventional shaft and sprocket assembly is very time consuming and oftentimes takes the combine out of production during the brief time window available for harvesting a crop.
Conventional shaft and sprocket assemblies generally have one of two designs. In one design, the sprockets are welded to the shaft. For this type of shaft and sprocket assembly, the entire shaft and sprocket assembly must be replaced. This requires significant disassembly and reassembly of the feederhouse. It also necessitates replacing the entire shaft and sprocket assembly when only one sprocket is damaged. FIGS. 1-3 illustrate an example of this type of design. The design includes a cylindrical sleeve 20 forming a hub from which a geared plate 22 projects to form the sprocket. The cylindrical sleeve 20 is slid onto a cylindrical shaft 24 and welded to the shaft 24 at the desired location. The example depicted in FIG. 3 has three sprockets mounted on a shaft.
Another type of shaft and sprocket assembly commonly used in feederhouse designs is the use sprockets having a non-circular central opening that is slid onto a non-circular shaft. The use of a non-circular shaft and sprocket opening forms a key and keyway type arrangement and allows for the transfer of torque from the shaft to the sprocket. FIG. 4 presents a view of a sprocket 26 having a sleeve defining a non-circular opening 28 that mates with a non-circular shaft 30 (FIG. 5). Significantly more machining is required to form a non-circular shaft 30 in comparison to a circular shaft of the same length.
When a sprocket similar to that depicted in FIG. 4 fails, it is only necessary to replace the damaged sprocket while the undamaged sprockets and the shaft (if undamaged) can be reused. The shaft and sprocket assembly, however, must still be entirely removed from the feederhouse for the damaged sprocket to be removed and for the new sprocket to be installed. This is because the sprockets must be slid off one end of the shaft to be removed and slid onto the shaft from one end and longitudinally along the shaft to the desired location on the shaft during installation.
Feederhouse shafts having sprockets mounted thereon typically have one end that is rotatably supported on a pillow block bearing and an opposite end that is engaged with a gear box that rotatably drives the shaft. Removing the shaft typically involves removing the pillow block bearing and disengaging the shaft from the gear box. This process takes a significant amount of time and generally requires skilled labor oftentimes requiring that the machinery be brought to a dealership to remove and reinstall a shaft instead of performing this maintenance operation in the field.
Thus, both of the most common prior art sprocket and shaft arrangements for combine feederhouses require the removal of the shaft and, consequently, remove the combine from production for a significant amount of time to effect the necessary repairs.
Improvements which reduce the downtime associated with the repair of a damaged sprocket are desirable.